Environmentalists on Friday made good on threats to sue organizers of the July 4 fireworks show in La Jolla, hoping to stop the 25th annual event in the name of reducing water pollution caused by pyrotechnics.

Supporters of the show have said for weeks that they will carry on despite legal threats by attorney Marco Gonzalez, who maintains that protecting water quality is his patriotic duty.

“It’s going to be quite a wonderful show and it would be nice if Mr. Gonzalez would stop using the media for self-promotion and come down and enjoy the show,” said Deborah Marengo, a founder of the nonprofit La Jolla Community Fireworks Foundation.

Marengo said the La Jolla foundation had lined up a pro bono attorney in anticipation of a courtroom showdown.

“We have the resources to secure that the La Jolla fireworks show will continue,” she said, adding that the event costs about $25,000 annually.

Gonzalez represents the Encinitas-based Coastal Environmental Rights Foundation, which recently finalized an agreement with producers of Big Bay Boom that allows the 10th annual event in San Diego Bay to proceed in exchange for the coordinator doing some tests and cleanup.

He has said the La Jolla fireworks spectacle is his top concern because it takes place near one of the most biologically important marine areas in California. In an e-mail sent to the La Jolla Community Fireworks Foundation on Tuesday, he made it clear that he wasn’t looking for a compromise.

“Unfortunately, unlike the other displays that are slated to take place over or near the water, we do not believe the La Jolla show can legally continue,” Gonzalez said. “Hence, the result of any discussions will only be to help you understand our position and possibly avoid the need to file suit.”

The lawsuit, filed in San Diego Superior Court, names the foundation, the nonprofit group Promote La Jolla and the city of San Diego, which environmentalists contend has improperly approved fireworks shows at La Jolla Cove.

“We would have preferred not to have to sue the city over this issue, but it totally refuses to follow the law,” said Sara Honadle, programs director for the Coastal Environmental Rights Foundation.

Alex Roth, a spokesman for Mayor Jerry Sanders, called the suit a baseless attempt to collect attorney’s fees.

“The city has no plans to stop issuing July Fourth fireworks permits just because a lawyer decides to sue,” Roth said. “What’s next? Will (Gonzalez) sue the city for allowing people to swim in the ocean while wearing sunscreen lotion?”

Environmental concerns about fireworks fouling water have been simmering for years. They came to the forefront in December, when Gonzalez’s legal challenges resulted in the cancellation of a New Year’s Eve pyrotechnic show in San Diego Bay.

Fireworks release several types of contaminants and debris including copper, fuses, cardboard and sulfate, according to the San Diego Regional Water Quality Control Board.

That agency polices water pollution in the region and has said groups discharging fireworks over bodies of water need a pollution permit. The board’s officials aim to complete a general-permit application for fireworks dischargers by early 2011. Getting approval for a fireworks show over water is expected to include monitoring and cleanup plans.

Until a permit is developed, water quality officials said they don’t plan to penalize groups or companies that shoot fireworks along the coast as long as they minimize the environmental harm.

Sandy Purdon, founder and executive producer of the Big Bay Boom, said his show will be held as planned at 9 p.m. on July 4 after successful negotiations with Gonzalez. Proceeds from sponsorships of the annual event benefit the San Diego Armed Services YMCA.

Purdon has agreed to test the waters around fireworks barges for metals and perchlorate salts. He said the program will cost a “couple thousand dollars” and the test results will be made public. His group also will remove trash and debris from the bay.

“I think it came out reasonable,” Purdon said. “We always intended to have a clean and safe show and adhere to all of the requirements from the government agencies, which we have done.”